The study has two major objectives: 1) To investigate the prevalence of behavioral, emotional, and cognitive dysfunction in representative urban and suburban populations of four-year-old children who will receive a battery of tests through mandatory screening; and (2) to develop an efficient, economical, and accurate method of screening that can be generalized to local and national populations. One sample of 150 high risk and 150 normal randomly selected four- year-old children screened from 1973-75 will be followed to determine the efficiency and accuracy of screening methods employed. In 1976, a revised series of measures will be created and will be applied to an additional population of 1,100 urban four-year-olds and 700 suburban children for a three-year period. Analysis will include the description of dysfunction present in the populations and comparison of prevalence by socio-economic and ethnic groups. The ultimate aim is to create an economical and efficient procedure that can aid in early identification of mental health problems and result in appropriate and timely intervention.